Spain's air traffic controllers say they are sticking to their threat to hold a partial strike in June just as the summer vacation season gets underway since no agreement has been reached to resolve the issue. The strike is expected to cause major travel disruptions.

The USCA controllers' trade union — which called the strike last month over penalties imposed on members who held a strike in 2010 — says Sunday the stoppage affects flights between 10 a.m.-to-noon and 6-8 p.m. on June 8, 10, 12 and 14.

The strike threatens 5,300 flights that week and could trigger airport chaos similar to a 24-hour wildcat strike in 2010 that stranded 600,000 passengers ahead of a national holiday.

Spain's government guarantees a minimum service of 70 percent of flights.